One of the most perplexing aspects of Confucianism is that people easily misunderstand it as a 100% humanism. An example is that, when early Jesuit missionaries went to China and found Zhu Xi's Neo-Confucianism of "Pattern-Principle" (理）and "Matter-Energy" (氣）was taken to be orthodox by Confucian elite, they categorized Confucianism as a form of "atheism" and thus thought it deeply corrupted.
In Christianity, even love towards one's neighbors is ultimately driven by divine grace. That means it is God who commands and makes us love our neighbors. However, because Confucianism lacks this kind of "divine agency" concept, it is very hard for Confucians to say when we love our parents and kids, it is ultimately and exclusively "Heaven" (天） who drives us towards this love.
The divergent situation is that Heaven in Confucianism is an all-encompassing constantly creative cosmic power. It lacks the Christian feature of "agency." The Heavenly creation is spontaneous, natural, and if we use a term in modern control theory, it can also be self-organized in certain circumstances such as on the earth, but there is no guarantee that every creation of Heaven is ordered according to human expectation. Since Heaven is constantly creating, the essence of human beings, as an organic part of Heaven, is also constantly creating. This constantly creating human nature is named by "Ren" (仁) in Confucianism. An impressive allegory made by Neo-Confucianism is that this human nature "Ren" embodied in humans is like the "kernel" (果仁）contained in the nutshell (果壳), so represents the essential of life. But what is distinct in Confucianism is, Heaven provides the creative energy to human beings, but how humans, as an "agent", use this energy is solely due to themselves.
As a matter of fact, when Confucians feel united with Heaven through an arduous process of self-cultivation, they would love a myriad of things under Heaven. But in this mystical situation, we can say, the great body of ours which we form with Heaven makes us want to love, but how to love concretely is still exclusively due to ourselves. In this way, the idea of "Heaven" as the divine reality in Confucianism provides ultimate axiological and aesthetic motives for humans' universal love, but it can't provide the "agency" which is the last crucial link leading to a concrete action of human love.
In this sense, it is wrong to characterize Confucianism as an "atheism", since "Heaven" is indeed the divine reality which provides the ultimate axiological and aesthetic values to human deeds. But it is not a "theism" too, since "Heaven" is not a personal God and lacks the Christian-like "agency". In fact, It is a non-theism. What Confucians worship about "Heaven" is a benevolent but wild cosmic creative power, without any anthropomorphic sort of purpose, will or plan. Correspondingly, the Confucian humanism is a non-theistic humanism, and in this strictly defined sense, it is a religious humanism.